This disclosure relates generally to methods and apparatus for expanding a tubular member in a wellbore. More specifically, this disclosure relates to expanding a tubular member using an adjustable expansion cone.
Wellbore tubular members, such as casings or liners, can be expanded in the wellbore using a variety of known processes. These processes often utilize expansion cones that are shaped to radially expand the tubular as the cone moved axially through the tubular. Many conventional expansion cones have a fixed outer diameter that is larger than the outer diameter of tubular member before expansion. The size of the fixed diameter expansion cone necessitates that, before expansion begins, the cone is contained within an enlarged section of the tubular, known as a launcher, or disposed outside of the tubular being expanded.
The launcher, or the expansion cone itself, is thus the component of the tool string having the largest outer diameter and is therefore a major factor in determining the operating envelope of the system. For example, if an expandable tubular is needed at a location in the wellbore below a restriction, the size of the launcher or cone will limit the systems that can be used. Fixed diameter cones are also susceptible to getting stuck in the unexpanded tubular should the expansion process fail or an unexpected restriction be encountered.
Adjustable expansion cones have been used to overcome some of the limitations of fixed diameter cones by providing a mechanism for varying the outer diameter of the cone. Adjustable expansion cones generally include a plurality of segments that are “assembled” downhole into a cone capable of expanding a tubular member. Adjustable cones are available in a variety of styles and configurations but, like conventional fixed diameter cones, suffer from certain performance limitations.
One issue that has limited the use of adjustable cones is the force needed to assemble the cone. If the cone is assembled in the tubular, the force needed to assemble the cone while simultaneously expanding the tubular can be significant. Previous systems have addressed this issue by including specialized force generators to provide the needed force and/or assembling the cone within a thin-walled section of the tubular in order to reduce the forces required. Certain systems include mechanisms to extend the adjustable cone out of the lower end of the tubular so as to assemble the cone in the open wellbore and avoid the problems caused by assembling the cone and expanding the tubular simultaneously. Each of these solutions adds complexity and costs to the expansion system.
Thus, there is a continuing need in the art for methods and apparatus for adjustable expansion cones that overcome these and other limitations of the prior art.